JPH1012955A - Method and apparatus for measuring optical fiber amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus for optical fiber amplifier in which a signal light having same level can enter into an optical fiber amplifier to be measured for each wavelength at the time of WDM(wavelength division multiplexing) measurement and a high power signal light can enter into the optical fiber amplifier to be measured at the time of measurement with input of single wavelength. SOLUTION: A measuring light signal delivered from a light source 1 is transmitted to an acoustooptic converter 3 through an optical fiber line 2 inserted with an optical fiber amplifier 12 and an optical switch 11 for short- circuiting the optical fiber selectively in parallel with each other. A measuring light signal delivered from the acoustooptic converter 3 is split through a photocoupler 5 into first and second optical signals. An optical switch 7 is fed with the first optical signal and the second optical signal amplified through an optical fiber amplifier to be measured. Any one of the first or second optical signals selected by the optical switch 7 is then modulated through an acoustooptic modulator 8 and an optical signal delivered therefrom is measured by means of a light spectrum analyzer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier measuring apparatus and a measuring method for measuring various characteristics of an optical fiber amplifier.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing the configuration of a conventional optical fiber amplifier measuring device. In FIG. 2, 50
Is a light source. The output light of the light source 50 is input to an optical fiber amplifier 52 via an optical fiber line 51, where it is amplified and supplied to an acousto-optic modulator 53. A modulation signal (for example, a low-frequency sound signal) is also input to the acousto-optic modulator 53, but illustration and detailed description thereof are omitted here.

[0003] An optical connector 54 is inserted into an intermediate portion of the optical fiber line 51, but a description thereof will be omitted. Further, hereafter, description of the same components will be omitted.

The optical signal output after being given a predetermined intensity modulation by the acousto-optic modulator 53 is split into two (optical power is 1: 1) by the optical coupler 55. One of the optical signals is input to the measured optical fiber amplifier 56 and amplified with a predetermined gain.

The other of the optical signals split by the optical coupler 55 and the optical signal amplified by the measured optical fiber amplifier 56 are input to an optical switch 57. The input terminal 57 _-1 of the optical switch 57, optical coupler 55
The optical signal divided by the
7 _-2 optical signal amplified by the measured optical fiber amplifier 56 is input.

[0006] The optical switch 57 selects one of input optical signals input optical signal to the input terminal 57 _-2 input terminal 57 _-1 from the output terminal 57 _-3.

The optical signal output from the optical switch 57 is
The signal is input to the acousto-optic modulator 58, given predetermined intensity modulation, and output. A modulation signal is also input to the acousto-optic modulator 58, but illustration and detailed description are omitted.

Reference numeral 59 denotes an optical spectrum analyzer.
This is for measuring the optical power of each unit described above. Reference numeral 60 denotes a reference optical power meter for calibrating the optical spectrum analyzer 59.

Next, a method for measuring an optical fiber amplifier by the optical fiber amplifier measuring apparatus shown in FIG. 2 will be described.
The method of measuring the optical fiber amplifier having the configuration shown in FIG. 2 is called an “optical method”.

[0010] In the optical method, first, the optical spectrum analyzer 59, the signal light power input to the optical fiber amplifier 56 P _in the signal light power P _out after being amplified by the measured optical fiber amplifier 56, further measured The power (spontaneous emission light power) _Pase of the spontaneous emission light (ASE light) output from the optical fiber amplifier 56 is measured.

[0011] Then, to calculate the gain G and noise figure NF of the measured optical fiber amplifier 56 based on the signal light power P _in and the signal light power P _out and the spontaneous emission light power P _ase. This calculation formula is as follows.

G = (P _out −P _ase ) / P _in (1) NF = (P _ase / h · ν · G · Δν) + (1 / G) (2) In the equation (2), h is Planck's constant, ν is the optical frequency of the optical signal, and Δν is the measurement resolution of the optical spectrum analyzer 59.

FIG. 3 shows the above-mentioned signal light powers P _in and P in.
acousto-optic modulator 53 and acousto-optic modulator 5 when measuring _out
FIG. 9 is a diagram showing a phase relationship with the reference numeral 8. When measuring the signal light powers P _in and P _out , the output light of the light source 50 is amplified by the measured optical fiber amplifier 56 and the measured optical fiber amplifier 5 is amplified.
The power of each signal light before and after being input to 6 is measured. Therefore, as shown in FIG. 3, the phase relationship between the acousto-optic modulator 53 and the acousto-optic modulator 58 is set to the same phase.

FIG. 4 is a diagram showing the phase relationship between the acousto-optic modulator 53 and the acousto-optic modulator 58 when measuring the spontaneous emission light power _Pase . The spontaneous emission light power _Pase is the power of the spontaneous emission light component (continuous light) output from the measured optical fiber amplifier 56. Therefore, to measure this,
It is necessary to create a state in which no signal light is input to the measured optical fiber amplifier 56. For this reason, the phase relationship between the acousto-optic modulator 53 and the acousto-optic modulator 58 is set to the opposite phase as shown in FIG. 4, and the power when the signal light is not supplied to the optical fiber amplifier 56 to be measured is measured. I do.

When measuring the characteristics of the optical fiber amplifier 56 to be measured, it is necessary to assume that the wavelengths of light are multiplexed and input. Referring to FIG. 5, a WDM (Wavelength Division Multiple) in which light wavelengths are multiplexed will be described below.
xing) Signal measurement (WDM measurement) will be described.

[0016] In the example shown in FIG. 5 is intended to enter the four-wave, 41 _-1 to 41 _-4 is a light source for outputting each different optical signal of the wavelength lambda ₁ to [lambda] _4. The optical signals output from the light sources 41 _{-1 to} 41 _-4 correspond to the corresponding optical attenuators 42 _-1 to 42 _-4.
The signal light level is adjusted by 2 _-4.

Thereafter, each signal light is converted to optical couplers 43 _-1 to 43 _-1.
-3 , and input to the optical fiber amplifier 52 as a WDM signal. The configuration after the optical fiber amplifier 52 is as shown in FIG. 2. By measuring the output light, the gain G and the noise figure NF of each wavelength are calculated based on the above equations (1) and (2). I do.

[0018]

At the time of WDM measurement in the above-mentioned conventional technique, the optical attenuators 42 _{-1 to} 42 _{-4 are used.}
Thus, the signal light power of each wavelength is adjusted, so that the signal light intensity for each wavelength is constant as shown in FIG.

The gain of the optical fiber amplifier 52 has wavelength dependence as shown in FIG. Therefore, signal light having different intensities for each wavelength is input to the measured optical fiber amplifier 56 as shown in FIG.

That is, if the optical fiber amplifier 52 is not inserted, each wavelength can be input at the same level. However, at the time of the characteristic measurement when one wavelength is input, the optical power is not amplified unless the optical fiber amplifier 52 is inserted, so that the input power to the fiber amplifier 56 to be measured becomes small, and accurate characteristic measurement cannot be performed.

The present invention has been made under the above-described background. In the WDM measurement, the same level of signal light can be input to the optical fiber amplifier under measurement for each wavelength, and the measurement at the input of one wavelength is performed. It is an object of the present invention to provide an optical fiber amplifier measuring apparatus and a measuring method capable of inputting a high power signal light to an optical fiber amplifier to be measured.

[0022]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, there is provided a light source for generating a measurement light signal used for measuring characteristics of an optical fiber amplifier to be measured; First modulation means for modulating the measurement light signal, an optical transmission line for transmitting the measurement light signal from the light source to the first modulation means, and a front optical fiber inserted in the transmission line in parallel with each other First selecting means for selecting whether or not the amplifier and the pre-optical fiber amplifier are to be short-circuited; and a measuring optical signal output from the first modulating means as a first optical signal and a second optical signal. An optical coupler that splits the optical signal into a plurality of optical signals, and a second optical signal that selects one of the first optical signal and the second optical signal amplified by the optical fiber amplifier under test.
Selecting means, a second modulating means for modulating either the first or second optical signal selected by the second selecting means, and an optical signal output by the second modulating means. Light measuring means for measuring. According to the second aspect of the present invention, in the optical fiber amplifier measuring apparatus according to the first aspect, the light source outputs a single-wavelength measurement optical signal, and the first modulating means includes the first modulation means. The measurement optical signal amplified by the pre-optical fiber amplifier is supplied. Claim 3
According to the invention described in (1), in the measuring device for an optical fiber amplifier according to claim 1, the measurement optical signals output from the light source include optical signals of a plurality of wavelengths each having a uniform intensity, and the first The selecting means short-circuits the front optical fiber amplifier.

In the invention according to claim 4,
A first selection for outputting a measurement optical signal used for measuring characteristics of an optical fiber amplifier to be measured from a light source and selecting whether or not to short-circuit the pre-optical fiber amplifier and the pre-optical fiber amplifier inserted in parallel with each other. Transmitting the measurement optical signal to a first modulating means through an optical transmission line having
The optical signal is divided into a first optical signal and a second optical signal by the optical coupler, and the second selecting means selects one of the two input optical signals. The first optical signal and the second optical signal amplified by the measured optical fiber amplifier are supplied to an input terminal, and the first or second optical signal selected by the second selecting means is supplied to the input terminal.
The second modulation means modulates any one of the optical signals, and the optical signal output from the second modulation means is measured by the light measurement means. According to a fifth aspect of the present invention, in the method for measuring an optical fiber amplifier according to the fourth aspect, a single wavelength measurement optical signal is output from the light source, and the first modulating unit outputs the single wavelength measurement optical signal. The measuring optical signal amplified by the pre-optical fiber amplifier is supplied. According to a sixth aspect of the present invention, in the method for measuring an optical fiber amplifier according to the fifth aspect, the light source outputs a measurement optical signal including optical signals of a plurality of wavelengths each having uniform intensity. Wherein the first optical fiber amplifier is short-circuited by the first selecting means.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

A. Configuration An embodiment of the present invention will be described below. FIG.
FIG. 1 is a block diagram showing a configuration of an optical fiber amplifier measuring device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a light source. This light source
The output light from the optical connector 4 is_-1i, 4 _-1oOptical fiber with
The terminal 11 of the optical switch 11 is connected via the line 2_-2Enter
Is forced.

Thereafter, all optical signals are transmitted by the optical fiber line 2 as described above, but the illustration and detailed description of reference numerals are omitted in FIG.

This optical switch 11 has four terminals 1
1 _-1 , 11 _-2 , 11 _-3 and 11 _-4 , and connects between the terminals 11 _-1 and 11 _-4 and between the terminals 11 _-2 and 11 _-3 (solid line in the figure) connection) or can choose to connect between the terminals 11 _-1 and 11 _-2 and between terminals 11 _-3 and 11 _-4 (broken line in the drawing connection).

The terminal 11 of the optical switch _11-1 and the terminal 11 _-4
Is connected to the optical fiber amplifier 12.
The optical signal output from the terminal _11-3 of the optical switch 11 is
The signal is input to the acousto-optic modulator 3. Acousto-optic modulator 3
In addition, a modulation signal (for example, a low-frequency acoustic signal: not shown) is input to the optical signal, and a predetermined intensity modulation is applied to the optical signal and output.

An optical signal output from the acousto-optic modulator 3 is split into two by an optical coupler 5. Here, the optical coupler 5 divides the power of the input optical signal into 1: 1. One of the optical signals is input to the optical fiber amplifier 6 to be measured via the optical connectors _{4-2 i} and _{4-2 o} , and is amplified with a predetermined gain.

The other optical signal divided by the optical coupler 5 described above are inputted directly to the input terminal _7-1 of the optical switch 7. The input terminal 7 _-2 one optical switch 7, the optical connector 4 _-3I, the optical signal amplified by the measured optical fiber amplifier 6 through 4 _-3O inputted.

The optical switch 7 selects one of input optical signals input optical signal to the input terminal 7 _-2 input terminal _7-1 from the output terminal 7 _-3.

The optical signal output from the optical switch 7 is input to the acousto-optic modulator 8 and given a predetermined intensity modulation to be output. A modulation signal is also input to the acousto-optic modulator 8, but illustration and detailed description thereof are omitted.

Reference numeral 9 denotes an optical spectrum analyzer for measuring the optical power of each unit described above. In FIG. 1, the optical spectrum analyzer 9 includes an optical connector 4 _-4i ,
It is connected to the output side of the acousto-optic modulator 8 via _4-4o . Reference numeral 10 denotes a reference optical power meter for calibrating the optical spectrum analyzer 9.

B. Measurement Method (a) WDM Measurement First, the procedure of measuring the characteristics of the measured optical fiber amplifier 6 using multiplexed signal light (WDM measurement) in the present embodiment will be described.

Here, it is assumed that the multiplexed signal light supplied to the optical fiber amplifier 6 to be measured has signal lights of wavelengths λ _{1 to} λ _n , and that the level of the signal light is uniform at each of the wavelengths λ _{1 to} λ _n . It is explained that there is something.

In the case of WDM measurement, first, the optical switch 11
Between the terminals 11 _-2 and 11 _-3 are connected. As a result, the acousto-optic modulator 3 is supplied with signal light of a uniform level at each of the wavelengths λ _{1 to} λ _n .

[0037] At this time, while the input terminal 7 _-2 optical switch 7 and the output terminal 7 _-3 in a connected state, the optical connector 4 _-6I alternately and the optical connector 4 _-5I and the optical connector 4 _-6O By connecting, the optical spectrum analyzer 9 is calibrated by the reference optical power meter 10.

Next, a modulation signal is supplied to the acousto-optic modulator 3 and the acousto-optic modulator 8 to be in a modulation state,
The mutual phases of the acousto-optic modulator 3 and the acousto-optic modulator 6 are set to the same phase.

[0039] For each of wherein the wavelength lambda ₁ to [lambda] _n, by connecting the input terminals _7-1 of the optical switch 7 and the output terminal 7 _-3 measure the signal light power P _in the optical spectrum analyzer 9, a light connect the input terminal 7 _-2 switch 7 and an output terminal 7 _-3 measuring the signal light power P _out.

Next, while the acousto-optic modulator 3 and the acousto-optic modulator 8 are in the modulated state, the mutual phases of the acousto-optic modulator 3 and the acousto-optic modulator 8 are set to opposite phases.
Wherein for each of the wavelength lambda ₁ to [lambda] _n, by connecting the input terminal 7 _-2 optical switch 7 and the output terminal 7 _-3, measuring the spontaneous emission light power P _ase by an optical spectrum analyzer 9.

[0041] Thereafter, by the signal light power P _in and the signal light power P _out and the spontaneous emission light power P _ase, based on the aforementioned equation (1) and (2), the wavelengths lambda ₁ to [lambda] _n
, The gain G of the measured optical fiber amplifier 6 and the noise figure NF are calculated.

(B) Single Light Measurement First, a procedure for measuring the characteristics of the measured optical fiber amplifier 6 with a single wavelength signal light (single light measurement) in this embodiment will be described.

In the case of single light measurement, first, the optical switch 11
Between terminals 11 _-1 and 11 _-2 , and terminals 11 _-3 and 1
_{Make a} connection between _1-4 . Thus, the acousto-optic modulator 3 is supplied with the high-power signal light amplified by the optical fiber amplifier 12.

It should be noted also in this case, with the input terminal 7 _-2 optical switch 7 and the output terminal 7 _-3 in a connected state, the optical connector 4 _-6I the optical connector 4 _-5I and the optical connector 4 _-6O By connecting them alternately, the optical spectrum analyzer 9 is calibrated by the reference optical power meter 10.

Next, a modulation signal is supplied to the acousto-optic modulator 3 and the acousto-optic modulator 8 to bring them into a modulation state.
The mutual phases of the acousto-optic modulator 3 and the acousto-optic modulator 6 are set to the same phase.

Here, the input terminal 7 of the optical switch 7_-1And out
Force terminal 7_-3To the optical spectrum analyzer 9
Therefore, the signal light power P_inIs measured, and the input terminal of the optical switch 7 is
Child 7 _-2And output terminal 7_-3And the signal light power P_outTo
Measure.

Next, the mutual phases of the acousto-optic modulator 3 and the acousto-optic modulator 6 are set to be opposite to each other while the acousto-optic modulator 3 and the acousto-optic modulator 8 are in the modulated state.
Here, by connecting the input terminal 7 _-2 optical switch 7 and the output terminal 7 _-3 measuring the spontaneous emission light power P _ase by an optical spectrum analyzer 9.

[0048] Thereafter, by the signal light power P _in and the signal light power P _out and the spontaneous emission light power P _ase, on the basis of the above-mentioned (1) and (2), of the measured optical fiber amplifier 6 The gain G and the noise figure NF are calculated.

In the present embodiment, WD
The gain G and the noise figure NF of the measured optical fiber amplifier are measured by M measurement or single light measurement.

[0050]

As described above, according to the present invention, a measuring optical signal used for measuring the characteristics of an optical fiber amplifier to be measured is output from a light source, and a pre-optical fiber amplifier inserted in parallel with the optical fiber amplifier is connected to the optical fiber amplifier. A measuring light signal transmitted to the first modulating means via an optical transmission line having first selecting means for selecting whether or not to short-circuit the optical fiber amplifier, and the measuring light output from the first modulating means. The signal is split into a first optical signal and a second optical signal by an optical coupler, and the first optical signal is input to an input terminal of a second selector for selectively selecting one of the two input optical signals. And the second optical signal amplified by the optical fiber amplifier under test, and the second modulator modulates either the first or second optical signal selected by the second selector. The optical signal output from the second modulating means is converted by the light measuring means. To measure Te. Further, a measurement light signal having a single wavelength is output from the light source, and the measurement light signal amplified by the optical fiber amplifier is supplied to the first modulation means. Alternatively, since the light source outputs measurement optical signals including optical signals of a plurality of wavelengths each having a uniform intensity and the first optical fiber amplifier is short-circuited by the first selecting means, the WDM
An optical fiber amplifier measuring device that can input the same level of signal light for each wavelength to the measured optical fiber amplifier at the time of measurement, and can input a large power signal light to the measured optical fiber amplifier at the time of one wavelength input. And an effect that the measuring method can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical fiber amplifier measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a conventional optical fiber amplifier measuring device.

FIG. 3 is a diagram showing a phase relationship between an acousto-optic modulator 53 and an acousto-optic modulator 58 when measuring signal light powers P _in and P _{out in a} conventional optical fiber amplifier measuring apparatus.

[Figure 4] when measuring the spontaneous emission light power P _{the as e} in the measurement apparatus of the conventional optical fiber amplifier is a diagram showing a phase relationship between the acousto-optic modulator 53 and acousto-optic modulator 58.

FIG. 5 is a configuration diagram showing a configuration example in the case of WDM measurement in a conventional optical fiber amplifier measurement device.

FIG. 6 is a diagram showing the intensity of signal light for each wavelength of a WDM wave in the measurement of the conventional optical fiber amplifier for WDM measurement.

FIG. 7 is a diagram showing the wavelength dependence of the gain of the optical fiber amplifier 52.

8 is a diagram showing the intensity of signal light for each wavelength of a WDM wave output from the optical fiber amplifier having the gain characteristic shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 light source 2 optical fiber line (optical transmission line) 3 acousto-optic modulator (first modulation means) 5 optical coupler 6 optical fiber amplifier to be measured 7 optical switch (second selection means) 8 acousto-optic modulator (second) 9) Optical spectrum analyzer (optical measuring means) 11 Optical switch (first selecting means) 12 Optical fiber amplifier (pre-optical fiber amplifier)

Claims (6)

[Claims] 1. A light source (1) for generating a measurement light signal used for measuring characteristics of an optical fiber amplifier under test (6), and a first modulation means (3) for modulating the measurement light signal.
An optical transmission line (2) for transmitting the measurement optical signal from the light source to the first modulation means; a front optical fiber amplifier (12) inserted in parallel with the transmission line; First selecting means (11) for selecting whether or not to short-circuit the fiber amplifier; and dividing the measuring optical signal output from the first modulating means into a first optical signal and a second optical signal. An optical coupler (5); and second selecting means (7) for selecting one of the first optical signal and the second optical signal amplified by the optical fiber amplifier under test. A second modulating means for modulating either the first or second optical signal selected by the second selecting means; and measuring an optical signal output by the second modulating means. Optical fiber amplifier comprising: Measuring device. 2. The apparatus according to claim 1, wherein the light source outputs a measurement light signal of a single wavelength, and the first modulation means is supplied with the measurement light signal amplified by the pre-optical fiber amplifier. An optical fiber amplifier measuring device according to claim 1. 3. The measuring optical signal output from the light source includes optical signals of a plurality of wavelengths each having a uniform intensity, and the first selecting means short-circuits the pre-optical fiber amplifier. An optical fiber amplifier measuring device according to claim 1. 4. A measurement light signal used for measuring characteristics of an optical fiber amplifier to be measured is output from a light source, and a selection is made as to whether or not the pre-optical fiber amplifier inserted in parallel with the pre-optical fiber amplifier is short-circuited. Transmitting the measurement light signal to the first modulation means via an optical transmission line having a first selection means for performing the measurement, and outputting the measurement light signal output from the first modulation means to the first optical signal by an optical coupler. And a second optical signal. The first optical signal and the measured optical fiber amplifier are amplified by an input terminal of a second selecting means for selectively selecting one of the two input optical signals. And the second optical signal selected by the second selecting means, and the second or third optical signal is modulated by the second modulating means. The optical signal output from the modulating means is Measurement method for the optical fiber amplifier, characterized by a constant. 5. A measurement light signal having a single wavelength is output from the light source, and the measurement light signal amplified by the front optical fiber amplifier is supplied to the first modulation means. Item 5. The method for measuring an optical fiber amplifier according to Item 4. 6. The method according to claim 1, wherein the light source outputs measurement optical signals including optical signals of a plurality of wavelengths each having a uniform intensity, and the first optical fiber amplifier is short-circuited by the first selecting means. A method for measuring the optical fiber amplifier according to claim 5.